A comparative study of kiwifruit produced under three farming systems (conventional, organic and integrated)

Laburpena

The environmental problems related with kiwifruit production based on conventional farming systems have moved society, consumers and producers to the beginning of a change in philosophy away from purely production-oriented practices towards those that are more environmentally sustainable. Then, new alternative farming systems have emerged, being in Spain integrated and organic farming systems the most important ones. While integrated farming systems involve hence lower inputs of fertilisers and reduced application of biocides, organic system is characterised by the absence of synthetic fertilisers and pesticides. The main aim of this PhD Thesis was to investigate the effect of three farming systems: conventional, integrated and organic on kiwifruit growth, development and production. To achieve this objective three kiwifruit orchards, with three different management systems (conventional, integrated and organic), located in a homogeneous climatic zone were studied. Also the influence of climate conditions changes, among seasons, was investigated. Mineral nutritional status (in soil, leaves and fruits), phenological events (budbreak, flowering, fruit set, growth and harvest), fruit production and fruit quality were determined, monitored and statistically analyzed. Results demonstrated a statistical effect of farming systems and climatic conditions on kiwifruit growth and development. Regular application of lime and organic matter (manure compost and plant wastes) to organic systems, turned essential to increase soil pH and effective cation exchange capacity maintaining soil fertility, favoring plant nutrition, providing better soil properties and fruit mineral content. Furthermore, organic farming systems showed the greatest budbreak and flowering indexes, and commercial fruit production (per square meter of vine). Hydrogen cyanamide was exclusively applied to integrated farming systems, causing the earlier budbreaking onset, anthesis, final flowering and bigger size fruits compared to conventional and organic systems. However the application of hydrogen cyanamide worsened the production rates due to increased the risk of bud frost damage as described here. Finally, conventional orchards showed the lowest soil pH, the highest hydrogen and aluminium values, which could displace exchangeable cations from the soil complex and favoured cations losses by leaching, and as results, showed the lowest effective cation exchange capacity and poorest soil properties. Conventional fruit production was not signicantly different from integrated systems. Finally, climatic factors played a very important role in budbreak, flowering and production events during kiwifruit development. Although climatic conditions seems to be adecuate for kiwifruit culture, low temperatures and high rainfall during budbreak and flowering caused an unfavourable conditions for achieve high fruit productions as those described here during the second season studied